The current price of a forever stamp is $.60 but the value goes up if the postage rate goes up. That is why they are forever. I am still working thru the shoebox full of stamps that I got at yard sales so I won't be worrying about forever stamps for a LONG time.

As far as the mailer, if it meets the dimension requirements then it could be shipped for $.60 except for the fact that the chip could be considered rigid which is why most everything that I ship I mark as "non-machinable" (rigid) and pay the $.39 added fee. Don't worry so much about what the shipping fee is versus actual postage. A lot of people charge less for their product and jack up the shipping fee to make up for it. So long as you are happy with the total cost it all works out.